Commitments and Contingencies (Details)	1 Months Ended	12 Months Ended
	Jul. 31, 2013	Jun. 30, 2016 USD ($) item	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Jun. 30, 2016 GBP (£) ft²	Jun. 30, 2016 USD ($) ft²	Feb. 29, 2016 USD ($) ft²	Dec. 31, 2015 USD ($)	Apr. 30, 2014 USD ($)	Dec. 31, 2013 USD ($)	Apr. 30, 2013 ft²
Operating leases
Construction allowance			$ 6,301,000			$ 6,236,000
Facilities rent expense, net of sublease income		$ 6,500,000	$ 6,000,000	$ 5,400,000
Minimum rental commitments under the non-cancelable operating lease agreements
2017						7,902,000
2018						8,056,000
2019						7,258,000
2020						7,254,000
2021						7,302,000
Thereafter						34,252,000
Total minimum lease payments						72,024,000
Total minimum rental payments from sublease						(250,000)
Total minimum lease payments, net						71,774,000
Obligations under capital leases						$ 0
Collaborations and Licenses
Potential milestone payable				162,000,000
Amount reimbursable by a third party				$ 1,400,000
Obligation to make payment to vendor for certain contractual services | £					£ 300,000
830 Winter Street, Waltham, MA
Operating leases
Area of space leased (in square feet) | ft²					110,000	110,000
Number of additional terms for which lease agreement can be extended | item		2
Lease term extension period		5 years
Construction allowance								$ 196,000	$ 1,100,000	$ 746,000
930 Winter Street, Walham, MA
Operating leases
Area of space leased (in square feet) | ft²							10,281
Construction allowance							$ 617,000
333 Providence Hwy, Norwood MA
Operating leases
Area of space leased (in square feet) | ft²					43,850	43,850
Lease term extension period		5 years
100 River Ridge Drive, Norwood, MA
Operating leases
Area of space leased (in square feet) | ft²											7,507
Lease term extension period	5 years
Lease term period	5 years 2 months